1. Field of the Invention
The present invention relates to security devices and particularly to automatic dead bolt locks. More specifically, this invention is directed to the accomplishment of an automatic dead bolting function, either alone or in combination with a hold back function, in a single lock. Accordingly, the general objects of the present invention are to provide novel and improved apparatus and methods of such character.
2. Description of the Prior Art
A tubular dead bolt lock which has enjoyed wide commercial success is disclosed in U.S. Pat. No. 4,272,974. A particularly important feature of the patented lock is the long bolt "throw", i.e., the large amount of linear motion imparted to the bolt in response to less than 180.degree. of rotation of the inside or outside actuator. Long bolt throw, i.e., at least one inch of linear motion, is considered essential in order for a dead bolt lock to provide adequate security. A disadvantage of the lock of U.S. Pat. No. 4,272,974, for some applications, resides in the fact that a deliberate manual operation is required in order to accomplish the deadlocking function. Another tubular dead bolt, having the same disadvantage, is disclosed in U.S. Pat. No. 4,333,324.
Automatic dead bolt locks have previously been proposed. Examples of such proposed designs may be seen from U.S. Pat. Nos. 4,561,684 and 4,671,549. The previously proposed automatic dead bolt locks have been characterized by one or more serious deficiencies. A first of these deficiencies is short, i.e., less than one inch, bolt throw. Another common problem is that the lock, when set in the "armed" position, has the bolt fully retracted. Thus, a closed but not dead locked door may simply be pushed open. An additional disadvantage of prior dead bolt locks has been a lack of versatility. Thus, there has not previously been available a dead bolt lock assembly which could be installed without modification on left or right hand doors and/or on reverse bevel doors.